Hi Tom. It's difficult to address your issue without actually being there. We've heard of this issue in the past and just inserting a magazine makes the rattle stop. That being said I don't think the magazine should be responsible for making the gun tight.
The one's I've heard about in the past suffered no accuracy issues so you might be ok.
This is something that if it's bad enough you might want to run by Kahr customer service. Send them an email, express your concern. Can you wiggle the slide on the frame considerable, side to side and / or up and down?
In Memory of Paul "Dietrich" Stines.
Dad: Say something nice to your cousin Shirley
Dietrich: For a fat girl you sure don't sweat much.
Cue sound of Head slap.
RIP Muggsy & TMan
"If you are a warrior legally authorized to carry a weapon and you step outside without that weapon, then you become a sheep, pretending that JOCKO will not come today."